migrate to nvim_buf_set_text

[numToStr]

Currently, nvim_buf_set_lines() is used which should be replaced with nvim_buf_set_text().

Why?

This is from :h nvim_buf_set_text()

                This is recommended over nvim_buf_set_lines when only
                modifying parts of a line, as extmarks will be preserved on
                non-modified parts of the touched lines.

How?

Currently, comment/uncomment is done by slicing, dicing, and modifying the lines. Because of this we only had to care about line numbers or rows. But for nvim_buf_set_text() we also need to consider the start and end of the starting and ending column to perfectly place/remove the comments

[numToStr]

Sadly this won't preserve the ordinary marks

• Marks disappear in un-/commented lines #24

[numToStr]

I am closing this for now. As it seems, this task is much more involved than I initially thought.